Brainmatters | Wintertime – our hope in dark times


Last weekend we could change our clocks back from daylight saving time. This allows us to still leave for university in daylight and to get out of bed a little less early. The feeling is correct: during winter, our internal clock is better synchronized with social clock time and we behave more in line with the rising and setting of the sun.

So for a little while, bringing science to young people before the clock has struck nine will feel a little less painful. These young people themselves should not even be in class before ten anyway. During adolescence our internal clock gradually shifts to a later time, so we are evening persons – ‘night owls’ – at our most extreme around our 20th birthday. This basically implies that we are brutally violating most students’ internal rhythms by expecting them to get out of bed in the middle of their biological night.

For them in particular, wintertime is bliss: one extra hour of sleep, plus a clock that’s better attuned to their internal clock. And frankly, looking at my colleagues and myself, this extra hour of night’s rest is not only doing them good. Most of us switch to wintertime – the ‘real’ time after all – swiftly and smoothly.

The real pain of daylight saving time comes in the spring. The German chronobiologist Kantermann and his colleagues from Groningen demonstrated in 2007 that this forward change of the clock has much worse repercussions and that some evening persons do not completely align with the clock throughout the summer. The first days after switching to daylight saving time also correlate with worse mood, more stress, a higher number of car accidents, and an increase of around 5% in heart attacks. And all this for an energy benefit that was never demonstrated and is fiercely disputed.

The good news is that the frequency of heart attacks shows a slight ‘dip’ after resetting the clock in autumn. We also sleep around 20 minutes longer in winter than in summer. So there is hope in these dark times: sleeping longer, getting up later; everything will be ok now – even if only for a little while.

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